Editor's note: Rep. Jared Polis, a Democrat, represents Colorado's 2nd Congressional District and is appearing in CNN.com's "Freshman Year" series along with Rep. Jason Chaffetz, a Republican from Utah.

Washington (CNN) -- I recently attended the White House Christmas tree lighting and congressional holiday party. Christmas is traditionally a time of peace and love, quite a juxtaposition for a nation fighting three wars, one in Iraq, one in Afghanistan, and a global war on terror.

We went into Afghanistan eight years ago to oust the Taliban and capture their guest Osama bin Laden and his al Qaeda associates. Eight years later, al Qaeda has largely been driven out of Afghanistan.

When should our nation go to war? Only as a last resort.

That's why I opposed the completely unnecessary invasion of Iraq, and why I now oppose an ongoing occupation of Afghanistan.

In meeting after meeting, I have been shown by generals and statesmen what we are doing in Afghanistan, how it could take decades, might not work, and is fraught with risks. In response, I ask the same repeated question: Why?

With all the ambiguity clouding the outcome, the case has not been conclusively made that the possibilities are more favorable with an increase of 30,000 troops.

The very real war on terror must be fought, not just in Iraq or Afghanistan, but across the globe. The terrorists, most notably al Qaeda and their associates, are a stateless menace.

With the manpower and financial resources we are putting into occupying the nation of Afghanistan, we could improve our port security, increase our intelligence gathering to locate and infiltrate terrorist cells, and increase our special operation capacity.

Three areas of focus -- homeland security, intelligence, and special operations -- are the three best tools in our toolbox to fight the war on terror. Focusing our resources on occupying a small mountainous Asian nation is peripheral at best and a lethal distraction at worst.

On military matters, I frequently turn to my colleagues who have more experience in the area, just as I hope they turn to me as it relates to education or small business issues.

My colleague Eric Massa from New York, one of the highest ranking retired officers now serving in Congress, stated my position far more eloquently and with more credibility than I ever could on a radio show last week: "If our security is at stake to the extent that we must rebuild a nation because there are 100 terrorists in Afghanistan, then we better be willing to occupy every single nation on the face of this planet and do the same.

"Our mission is to identify, locate, kill or capture, with malice of forethought, any terrorist anywhere. That does not call for a standing army of 100,000 people executing an occupational strategy in a foreign nation," Massa continued.

"We have tried this over and over and over again and it has never once worked. You cannot achieve this militarily. Period."

Before we send troops, we should truly know why we are doing it, and what their mission is.

Sending troops to capture bin Laden made sense. Had the intelligence reports indicating that he was acquiring nuclear weapons been accurate, going after Saddam Hussein could even have been justified.

Why are we bogging ourselves down in a country that is not a significant al Qaeda host at such great financial and human cost?

If Afghanistan were to become host to terrorist organizations, the answer would be targeted special operations to seek and destroy the terrorists, not embroiling the entire country in an interminable civil war and occupation.

In addition, our ongoing occupation increases the sympathy among some locals for the very terrorism we are there to fight.

The inevitable innocent casualties can turn neutral families into terrorist collaborators and America-haters.

The people that our soldiers are fighting day-in and day-out in Afghanistan are not terrorists.

It is unclear to me how spending $4 billion per month and putting tens of thousands of American lives at risk in Afghanistan is the best way to keep America safe from terrorist attack.

National security is neither partisan nor ideological. I am confident in saying that there isn't a Democrat or Republican in Congress today who doesn't want to protect our country from terrorists.

There is no conservative way to fight terrorists or liberal way to fight terrorists. Regardless of our party and ideology, every member of Congress needs to use the information we are privileged to receive to reach a conclusion as to the best way to protect our great nation from attack.

It is always difficult to oppose our commander in chief on such a vital national security issue, but I owe it to those who put me in office to use my best judgment using the best information I have.

I have done my due diligence, visited Iraq and Afghanistan, met with officers and statesmen, read the reports, and I cannot support sending a single additional American soldier to Afghanistan, much less 30,000.

The opinions expressed in this commentary are solely those of Rep. Jared Polis.